From the bench to the field: Hormonal regulation of plant senescence and environmental stresses
Plant senescence and shelf life of vegetables and fruits
Plant senescence is a genetically programmed process that involves the activation of senescence-associated genes (SAGs), resulting in the breakdown of cells and tissues. Our research has demonstrated that the leaf senescence program is regulated by plant growth substances: cytokinins delay this process, while ABA and ethylene accelerate it. Comparing intact leaf senescence to detached leaf senescence reveals similar morphological and biochemical changes, which pose agroeconomic problems. These issues include a short shelf life for fruits and leaves and yield decline due to early senescence. We have isolated a gene associated with early leaf senescence and designated it as the senescence-associated receptor kinase (SARK) based on its structure. Both the mRNA and the protein exhibit a characteristic temporal expression, indicating that SARK functions as an early senescence gene and may play a role as a senescence-regulated gene.
Development of delay senescence plants that also display extended shelf life of vegetable and fruits
We have designed an approach to create plants with delayed senescence by fusing the isolated promoter of the SARK gene to the key cytokinin biosynthesis gene, IPT. We hypothesized that activating the IPT gene during senescence would produce cytokinins and potentially delay the senescence syndrome. Indeed, the transgenic tobacco plants exhibited a dramatic delay in the senescence process, with yield increasing by almost twofold. Similarly, the shelf life of detached leaves was extended by 300%. These results suggest a biotechnological approach to increase crop yields and extend the shelf life of leaves and fruits.
Development of drought resistant plants
As a result of an accidental lack of watering, we surprisingly discovered that the transgenic plants developed to delay senescence demonstrated dramatic drought resistance. Further experiments revealed that these plants could grow without yield loss with as little as 40% of the optimal water supply. This scientific achievement may be employed for growing crops in semidry regions and may allow developing water saving plants for wide spectrum of varieties and species
